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Servo - Generic Continuous Rotation (Micro Size)

ROB-10189

Description: Here, for all your mechatronic needs, is a simple, high quality continuous rotation servo motor. This servo is able to take in 6 volts and deliver 30.6 oz-in. of maximum torque at 0.14 sec/60°

A standard 3-pin power and control cable is attached and all hardware listed below is included.

Please clarify what’s meant by “continuous full-rotation servo motor”. Is this a servo with a 360 degree range or is it a continuous rotation motor? <br />
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“Full rotation” and “360 degrees” are consistent with each other, but neither is consistent with “continuous”, as a “continuous” motor can turn an infinite number of degrees, not just one rotation.<br />
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Adding to the confusion is the “Rest point adjustment” claim. Although a servo, regardless of the number of degrees of its range, has a “rest point”, a continuous rotation motor does not.<br />
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TIA,<br />
Eric

Robert C.,<br />
<br />
Thanks!<br />
<br />
I see the “rest point” isn’t there any more, but the “360 degree” still is. <br />
<br />
Also, the description still says “servo”. If this were a servo motor, it would take a set point and adjust its position to be at the corresponding location, using internal feedback. If this is a continuous rotation motor, it takes a set point and scales its speed depending on that set point, but there’s no closed loop control, so it’s not a “servo”. This device may very well be in a package typical of servos and may even have been a servo before someone broke the feedback loop, but it’s not a servo if it’s continuous rotation, open-loop control.<br />
<br />
Eric

That might be true in a technical sense, but it is common practice in hobby robotics to modify servos by detaching the motion from the position potentiometer, thus closed-loop position circuitry becomes an approximate proportional velocity control.
I do not like the ambiguity of the term either, and I am not crazy about the accuracy of a hacked servo, even if they are, in this case, manufactured in this way - but its a cheap way to get decently controllable speed/heading for a differential drive robot.
Maybe a better name would be “Premodified continuous rotation servo” or something along that line for those shoppers who expect a very specific thing from the term “servo”

Normal Servo: give it 1.5ms pulse train and it will go to 90 degrees. Adjust the pulse to adjust the angle.
Continuous Rotation Servo: give it a 1.5ms pulse train and it will stop. Adjust the pulse to adjust the direction and speed.

I have 2 of these servos. While connected to an Arduino and the servo library
I wrote code where I could input value from keyboard(ms) and show value in serial console. Servo was moving accordingly
Servo library accepts millis as well as degrees inputs and to translate 180 degrees into millis you divide 500(ms) by 90(deg)
There you have 5,5ms = 1 degree movement = minimum speed of continuous servo
that was more or less the minimum required input to keep servo moving constantly.
//UndCon

I still can not get my servo to not move, it was like this when i got it. Adjusting the screw was probably a mistake, ( I am still a novice with micro controllers). I might just buy a regular servo seeing how that is all i need, unless i can interface this servo properly, would you mind sending me the code you made? You could put it on http://pastie.org/

Yes and No, since this is a full rotation servo setting the position does not work, so i use the servo library, and attach to pin 9, and then it just begins to spin, I have tried twisting the screw on the servo to adjust the hault position with no luck. I have also used http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1278145608 to try and interface it, but I can never find the hault position

that might be part of the problem. when i’ve used these, I just left them alone, used the servo library and when i told it to go to 90, it stayed still. when i told it to go 91, it moved slowly one way, and 89, slowly in the reverse direction. the further the number was from 90, the faster it went in that direction. you might have adjusted out a halt position. try writing a simple sketch that sweeps it, and see if it ever stops moving. for continuous rotation servos, you might want to use the write microseconds command as well.

When I just ran a test on my servo I purchased, I found that ‘center’ was actually 94. Not sure why the difference is, and don’t even see it as a problem, but am mentioning it here so no one gets discouraged if they experience different results. You just need to play with it to see what values do what for your servo.

Ok so now I am playing with the servo a few hours later, and find that the center point has moved to 93. Nothing changed except I unplugged the Arduino and waited a few hours. Not sure why this would be, but I can see this being a small problem in some applications.

I am not sure if detaching the servo is a good way to stop it in position or not, but plan on trying this as well.

“Torque: 3.3-4.8 kg/cm (4.8-6.0VDC respectively)"
I believe the unit you mean is kgcm, not kg/cm. 3.3 kgcm = 45.8 oz*in, which is average for an average servo. I’m buying four of them… will report performance soon.

If you are asking those questions you are looking for this servo: http://www.sparkfun.com/products/10333
which has an Operating speed of 0.18sec/60 degree (6V) and is a standard servo rather than continuous.

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